a) Field of the Invention
This invention relates to a new or improved snowmobile track belt suspension.
b) Description of the Prior Art
Snowmobile track belt suspensions often employ a slide frame pressed into contact with the upper side of the ground engaging run of the track belt loop by spring arrangements associated with suspension arm assemblies by which the slide frame is connected to the snowmobile chassis. Typically, two angulated arm assemblies are employed to connect the slide frame to the snowmobile chassis, and these arm assemblies are movable independently of one another to permit the slide frame to accommodate itself to static and dynamic forces arising in operation.
Irregularities in the terrain travelled by the snowmobile produce displacements and deflections of the snowmobile front suspension that supports the vehicle on the skis, and of the rear suspension. Depending upon their magnitude, frequency, and strength, these deflections cause more or less discomfort to the operator of the snowmobile. The present inventor theorizes that suspension displacements that produce angular acceleration of the snowmobile and its operator about a transverse horizontal axis produce more discomfort than displacements that merely produce vertical acceleration of the vehicle and its operator.
Accordingly it is an object of the invention to provide a snowmobile track belt suspension that will provide a reduced angular acceleration as compared to prior art snowmobile track suspensions.
The invention provides a snowmobile suspension comprising: a slide frame carried on downwardly and rearwardly angled front and rear suspension arm assemblies that are supported in the snowmobile chassis, said suspension incorporating spring means acting on said arm assemblies to urge said slide frame downwardly into contact with the ground-engaging run of the snowmobile track belt; said front and rear arm assemblies being substantially equal in length and generally parallelly arranged to position said slide frame substantially horizontally with respect to the snowmobile chassis; said frame arm assembly having upper and lower ends connected to fixed first and second pivots on the snowmobile chassis and on the slide frame respectively; said rear arm assembly having an upper end connected to a third fixed pivot on said snowmobile chassis, and having a lower end connected to a displaceable pivot that is movable longitudinally of said slide frame; movement of said displaceable pivot forwardly of said slide frame being limited by an abutment that is positioned so that the suspension arms form a parallelogram linkage, and which thus prevents the front end of the slide frame from moving to a higher position than the rear end thereof relative to said chassis; guide means on said slide frame adapted to accommodate movement of said displaceable pivot rearwardly away from said abutment to permit movement of the rear end of said slide frame to a higher position than the front end thereof relative to said snowmobile chassis.
With such an arrangement it is ensured that the loading imposed upon the track suspension by undulations in the terrain over which the snowmobile travels acts more on the front part of the track suspension than on its rear part, and thus effectively moves the average point of application of the vertical forces forwardly closer to the center of gravity of the vehicle, and accordingly reduces the resulted couple that produces the undesired angular acceleration.